1. Field of the Invention
This invention relates to a still camera provided with a film feeding device driven by an electric motor, and in particular to a device for controlling the feeding of a film.
2. Description of the Prior Art
Still cameras have become popular which are provided with an electric motor for driving a film feeding mechanism, whereby the operation of winding the leader portion of a roll film onto a take-up spool, the frame by frame wind-up operation after exposure and the operation of rewinding the film into a cartridge after termination of a rated number of exposures are automatic under the operative association with a photographing mechanism.
It is necessary to provide in such a still camera a countermeasure for immediately interrupting the power supply to the motor and thereby preventing the consumption of the battery when abnormality of the winding-up of the film occurs, for example, when the operation of an autoloading mechanism is incomplete and the leader portion of the loaded unexposed film fails to be wound on the spool and therefore the motor effects idle revolution or when the film reaches its limit of draw-out from the cartridge and therefore an overload occurs to stop the motor.
U.S. Pat. No. 4,400,074 discloses a device in which a switch is operatively associated with a free sprocket meshing with perforations and rotatable following the movement thereof so that each time one perforation is fed, the switch is changed over to reset a timer and if the time during which the free sprocket is not rotated exceeds the time required for one perforation to be fed, a time counting signal is put out from the timer to thereby cut off the power supply to the film winding-up motor. However, in the following case, a problem has occurred to this conventional device. That is, after a new film has been loaded into the camera, the motor is driven to wind the leader portion of the film on the spool. The film is moved only by the coupling of its leader portion to the spool with a result that the free sprocket is rotated. There is a time delay until this free sprocket is rotated. This is, for example, a case where the pawl of the spool does not immediately engage the perforation of the film but engages the perforation after the spool has made a certain degree of rotation or a case where the film is excessively drawn out from the cartridge and therefore the initial revolution of the motor is sent to eliminate the slack of this film. In such a case, a time counting signal has been put out from said timer before the film is fed and thus, the motor has been stopped without the film being fed.